In the upper part of the market of professional video cameras a triax system is used for transferring various signals back and forth over a coaxial cable between the camera and a base unit. Transferring multiple signals in different direction over a single cable is feasible because frequency multiplexing is used in which to every type of signal a separate frequency band is assigned.
In the lower part of the market a multi-core adapter solution is currently being used.
In earlier systems all signals were transferred as analogue signals over separate wires or cables. Because no frequency multiplex/de-multiplex is required such solution is much cheaper. However, a disadvantage is that the maximum distance between camera and base unit is restricted to about 100 meters, that the signals on the receiving side need to be equalized and that every additional meter of cable has a negative influence on the signal quality, e.g. the S/N ratio.
In current systems the analogue camera CVBS video output signal (Chroma Video Blanking Signal) is replaced by a standard serial SDI signal (Serial Digital Interface) achieving a maximum data rate of e.g. 270 Mbit/s, 143 Mbit/s, 360 Mbit/s or 540 Mbit/s for SDTV and 1.485 Gbit/s for HDTV over a coaxial cable. The SDI video signal has a word length of 10 bit and a multiplexed 4:2:2 format. Its clock rate is 27 MHz. It is standardized in ANSI/SMPTE 259 M and ANSI/SMPTE 125 M.
At the receiving base unit this SDI signal is re-clocked and/or converted to CVBS format or Y-Cr-Cb format. Thereby a degradation of the quality of the CVBS signal can be avoided. All the other signals in the multi-core cable remain in analog format.